The present invention relates to gas generating compositions that are loaded in gas generators to inflate occupant airbags of vehicles.
Sodium azide based gas generating compositions are well known. However, due to toxicity and handling difficulties of sodium azide, sodium azide-free gas generating compositions are needed. Preferably, the sodium azide-free gas generating composition is easily handled, burns at an appropriate rate without producing carbon monoxide and combustion residues, produces a sufficient amount of combustion gas to inflate the airbag within a fraction of a second, and is inexpensive.
In order to meet these requirements, ammonium nitrate-based gas generating compositions have been developed. For example, Japanese examined patent publication No. 6-69916 discloses a gas generating composition that includes ammonium nitrate, organic binder and plasticizer. Japanese unexamined patent publication No. 7-215790 discloses a gas generating composition that includes ammonium nitrate, thermoplastic elastomer containing binder, and glycidyl azide polymer containing plasticizer. Japanese unexamined patent publication No. 10-72273 discloses a gas generating composition that includes ammonium nitrate, reductant and combustion modifier. U.S. Pat. No. 3,954,528 discloses a gas generating composition that includes ammonium nitrate, triaminoguanidine nitrate and binder. U.S. Pat. No. 5,531,941 discloses a gas generating composition that includes ammonium nitrate and triaminoguanidine nitrate.
However, these ammonium nitrate based gas generating compositions have disadvantages. For example, the gas generating compositions of both Japanese examined patent publication No. 6-69916 and Japanese unexamined patent publication No. 7-215790 have a low burn rate and generate carbon monoxide. The gas generating composition of Japanese unexamined patent publication No. 10-72273 has a relatively high manufacturing cost due to the relatively expensive reductant. The gas generating compositions of U.S. Pat. No. 3,954,528 and No. 5,531,941 are difficult to handle due to the high impact sensitivity of triaminoguanidine nitrate.
The present invention addresses above disadvantages. It is an objective of the present invention to provide a gas generating composition that has an appropriate impact ignition sensitivity to allow easy handling of the gas generating composition, burns at an appropriate burn rate without producing a substantial amount of carbon monoxide and is inexpensive.
A gas generating composition of the present invention includes an oxidant and carbon powder that reacts with the oxidant. The oxidant is preferably ammonium nitrate. The carbon powder is preferably activated carbon powder.
The present invention further provides a method of preparing a gas generating composition that generates gas by a combustion reaction. The method includes mixing materials, which include oxidant and carbon powder. The mixing includes adding organic solvent to the materials to improve moldability of the mixture. The method further includes extruding the mixture into a predetermined shape.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.